Method for signaling control information, and apparatus therefor

ABSTRACT

The present invention relates to a wireless communication system. In detail, the invention relates to a method for a terminal to transmit a UCI in a carrier aggregation-based wireless communication system, and to an apparatus therefor, wherein the method involves the steps of: forming a first cell group having a PCell; forming a second cell group having one or more SCells; receiving one or more data in the second cell group; and transmitting HARQ-ACK information on the one or more data through a PUCCH, wherein, when the first and second cell groups are managed by an identical base station, the HARQ-ACK information is transmitted in the PCell, and, when the first and second cell groups are managed by different base stations, the HARQ-ACK information is transmitted in the second cell group.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/335,886, filed Jun. 1, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/006,656, filed Jun. 12, 2018, now U.S. Pat. No.11,064,469, which is a continuation of U.S. patent application Ser. No.15/652,040, filed Jul. 17, 2017, now U.S. Pat. No. 10,070,426, which isa continuation of U.S. patent application Ser. No. 15/332,638, filedOct. 24, 2016, now U.S. Pat. No. 9,788,307, which is a continuation ofU.S. patent application Ser. No. 14/418,855, filed Jan. 30, 2015, nowU.S. Pat. No. 9,504,029, which is the National Stage filing under 35U.S.C. 371 of International Application No. PCT/KR2013/006956, filed onAug. 1, 2013, which claims the benefit of U.S. Provisional ApplicationNo. 61/678,600, filed on Aug. 1, 2012, 61/750,306, filed on Jan. 8,2013, 61/807,785, filed on Apr. 3, 2013 and 61/822,310, filed on May 11,2013, the contents of which are all hereby incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for signaling controlinformation.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services such as voice or data. Ingeneral, a wireless communication system is a multiple access systemthat supports communication of multiple users by sharing availablesystem resources (a bandwidth, transmission power, etc.) among them. Forexample, multiple access systems include a Code Division Multiple Access(CDMA) system, a Frequency Division Multiple Access (FDMA) system, aTime Division Multiple Access (TDMA) system, an Orthogonal FrequencyDivision Multiple Access (OFDMA) system, and a Single Carrier FrequencyDivision Multiple Access (SC-FDMA) system.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the conventionalproblem is to provide a method and apparatus for efficientlytransmitting/receiving control information in a wireless communicationsystem, particularly a method and apparatus for efficientlytransmitting/receiving control information in inter-site CarrierAggregation (CA).

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In an aspect of the present invention, a method for transmitting UplinkControl Information (UCI) by a User Equipment (UE) in a wirelesscommunication system based on carrier aggregation includes configuring afirst cell group having a Primary Cell (PCell), configuring a secondcell group having one or more Secondary Cells (SCells), receiving one ormore data in the second cell group, and transmitting Hybrid AutomaticRepeat reQuest (HARQ)-ACKnowledgment (ACK) information for the one ormore data on a Physical Uplink Control Channel (PUCCH). If the firstcell group and the second cell group are managed by the same BaseStation (BS), the HARQ-ACK information is transmitted in the PCell, andif the first cell group and the second cell group are managed bydifferent BSs, the HARQ-ACK information is transmitted in the secondcell group.

In another aspect of the present invention, a UE for transmitting UCI ina wireless communication system based on carrier aggregation includes aRadio Frequency (RF) unit, and a processor. The processor is configuredto configure a first cell group having a PCell, configure a second cellgroup having one or more SCells, receive one or more data in the secondcell group, and transmit HARQ-ACK information for the one or more dataon a PUCCH. If the first cell group and the second cell group aremanaged by the same Base Station (BS), the HARQ-ACK information istransmitted in the PCell, and if the first cell group and the secondcell group are managed by different BSs, the HARQ-ACK information istransmitted in the second cell group.

If the first cell group and the second cell group are managed bydifferent BSs, the HARQ-ACK information may be transmitted in a SCell ofthe second cell group, in which the one or more data have been received.

If the first cell group and the second cell group are managed bydifferent BSs, the HARQ-ACK information may be transmitted in a SCellpredetermined for HARQ-ACK transmission in the second cell group.

If the first cell group and the second cell group are managed by thesame BS and data is received in two or more SCells of the second cellgroup, whole HARQ-ACK information for the two or more SCells may betransmitted in the PCell.

If the first cell group and the second cell group are managed bydifferent BSs and data is received in two or more SCells of the secondcell group, HARQ-ACK information for each of the SCells may betransmitted in the SCell.

Advantageous Effects

According to the present invention, control information can beefficiently transmitted/received in a wireless communication system.Particularly, control information can be efficientlytransmitted/received in inter-site CA.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present invention are not limited to whathas been particularly described hereinabove and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a configuration of an Evolved Universal MobileTelecommunications System (E-UMTS) network;

FIG. 2 illustrates configurations of an Evolved Universal TerrestrialRadio Access Network (E-UTRAN) and a gateway;

FIGS. 3A and 3B illustrate exemplary user-plane and control-planeprotocol stacks;

FIG. 4 illustrates a radio frame structure;

FIG. 5 illustrates a structure of an Uplink (UL) subframe;

FIG. 6 illustrates a slot-level structure of Physical Uplink ControlChannel (PUCCH) format 1a/1b;

FIG. 7 illustrates a slot-level structure of PUCCH format 1/2a/2b;

FIG. 8 is a diagram illustrating a signal flow for a random accessprocedure;

FIG. 9 illustrates an exemplary Uplink-Downlink (UL-DL) timingrelationship;

FIG. 10 is a diagram illustrating a signal flow for a handoverprocedure;

FIG. 11 illustrates an example of determining PUCCH resources forAcknowledgement/Negative Acknowledgement (ACK/NACK) transmission;

FIG. 12 is a diagram illustrating a signal flow for an ACK/NACKtransmission procedure in a single-cell situation;

FIG. 13 illustrates an exemplary Carrier Aggregation (CA) communicationsystem;

FIG. 14 illustrates an exemplary scheduling in the case where aplurality of carriers are aggregated;

FIG. 15 illustrates an example of allocating a Physical Downlink ControlChannels (PDCCH) to a data region of a subframe;

FIG. 16 illustrates a Medium Access Control (MAC) Packet Data Unit(PDU);

FIG. 17 illustrates a Secondary Cell (SCell) activation/deactivation MACControl Element (CE);

FIG. 18 illustrates a Timing Advance Command (TAC) MAC CE;

FIG. 19 illustrates a Power Headroom Report (PHR) MAC CE;

FIG. 20 illustrates exemplary inter-site CA;

FIG. 21 illustrates an exemplary signaling method/path according to anembodiment of the present invention; and

FIG. 22 is a block diagram of a Base Station (BS) and a User Equipment(UE) that are applicable to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following techniques disclosed below may be used for various radioaccess systems such as Code Division Multiple Access (CDMA), FrequencyDivision Multiple Access (FDMA), Time Division Multiple Access (TDMA),Orthogonal Frequency Division Multiple Access (OFDMA), and SingleCarrier Frequency Division Multiple Access (SC-FDMA). CDMA may beimplemented as a radio technology such as Universal Terrestrial RadioAccess (UTRA) or CDMA2000. TDMA may be implemented as a radio technologysuch as Global System for Mobile communications (GSM)/General packetRadio Service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMAmay be implemented as a radio technology such as IEEE 802.11 (Wi-Fi),IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA (E-UTRA), etc. UTRA is apart of Universal Mobile Telecommunications System (UMTS). 3^(rd)Generation Partnership Project (3GPP) Long Term Evolution (LTE) is apart of Evolved UMTS (E-UMTS) using E-UTRA, adopting OFDMA for Downlink(DL) and SC-FDMA for Uplink (UL). LTE-Advanced (LTE-A) is an evolvedversion of 3GPP LTE.

The embodiments of the present invention will be described below in thecontext that the technical features of the present invention are appliedto a 3GPP LTE/LTE-A system, for the clarity of description. However, itshould not be constructed as limiting the present invention. Specificterms as used herein are provided to help understanding of the presentinvention and may be replaced with other terms without departing thescope of the present invention.

Terms used in the present disclosure will first be described.

FIG. 1 illustrates a configuration of an E-UMTS network. The E-UMTS isalso called an LTE system. A communication network is widely deployedand provides various communication services such as voice and packetdata.

Referring to FIG. 1, the E-UMTS network includes an Evolved UniversalTerrestrial Radio Access Network (E-UTRAN), an Evolved Packet Core(EPC), and one or more User Equipments (UEs). The E-UTRAN may includeone or more evolved Node Bs (eNBs) 20 and a plurality of UEs 10 may belocated in one cell. One or more E-UTRAN Mobility ManagementEntity/System Architecture Evolution (MME/SAE) gateways 30 may belocated at an end of the network and connected to an external network.DL refers to communication directed from an eNB 20 to a UE 10 and ULrefers to communication directed from a UE 10 to an eNB 20.

A UE 10 is a communication device carried by a user and referred to as aMobile Station (MS), a User Terminal (UT), a Subscriber Station (SS), ora wireless device. An eNB 20 is generally a fixed station thatcommunicates with a UE and referred to as an Access Point (AP). The eNB20 provides user-plane and control-plane end points to the UE 10. OneeNB 20 may be deployed in each cell. An interface for transmitting usertraffic or control traffic may be used between eNBs 20. An MME/SAEgateway 30 provides an end point of a session and mobility managementfunction to the UE 10. The eNB 20 and the MME/SAE gateway 30 may beconnected to each other via an S1 interface.

An MME provides various functions including distribution of pagingmessages to the eNBs 20, security control, idle-state mobility handling,SAE bearer control, and cyphering and integrity protection of Non AccessStratum (NAS) signaling. An SAE gateway host provides various functionsincluding plane-packet termination and user-plane switching to supportthe mobility of the UEs 10. The MME/SAE gateway 30 will be referred toshortly as a gateway. However, it is to be understood that the MME/SAEgateway 30 covers both the MME and the SAE gateway.

A plurality of nodes may be connected via an S1 interface between an eNB20 and a gateway 30. eNBs 20 may be connected to one another via X2interfaces and adjacent eNBs 20 may be configured in a mesh network withX2 interfaces.

FIG. 2 illustrates configurations of a general E-UTRAN and a generalgateway 30. Referring to FIG. 2, an eNB 20 may perform functions such asselection of a gateway 30, routing to a gateway during Radio ResourceControl (RRC) activation, scheduling and transmission of a pagingmessage, scheduling and transmission of Broadcast Channel (BCCH)information, dynamic UL/DL resource allocation to UEs 10, configurationand preparation of eNB measurement, radio bearer control, RadioAdmission Control (RAC), and connection mobility control in LTE_ACTIVEstate. The gateway 30 may perform functions such as paging transmission,LTE_IDLE state management, user-plane encryption, SAE bearer control,and ciphering and integrity protection of NAS signaling.

FIGS. 3A and 3B illustrate user-plane and control-plane protocol stacksfor E-UMTS. Referring to FIGS. 3A and 3B, the protocol layers may bedivided into Layer 1 (L1), Layer 2 (L2), and Layer 3 (L3) based on thelowest three layers of the Open System Interconnection (OSI) referencemodel known in the field of communication systems.

The Physical (PHY) layer at L1 provides an information transfer serviceto its higher layer on physical channels. The PHY layer is connected toits higher layer, the Medium Access Control (MAC) layer throughtransport channels and data is transmitted between the MAC layer and thePHY layer through the transport channels. Data is transmitted betweenthe PHY layers of a transmitter and a receiver on physical channels.

At L2, the MAC layer provides a service to its higher layer, the RadioLink Control (RLC) layer through logical channels. The RLC layer at L2supports reliable data transmission. When the MAC layer takes charge ofthe RLC functionalities, the RLC layer is incorporated as a functionblock into the MAC layer. The Packet Data Convergence Protocol (PDCP)layer at L2 performs a header compression function. Owing to the headercompression function, Internet Protocol (IP) packets such as IPv4 orIPv6 packets can be efficiently transmitted via a radio interface havinga relatively narrow bandwidth.

The RRC layer at the lowest of L3 is defined only on the control plane.The RRC layer controls logical channels, transport channels, andphysical channels in relation to configuration, reconfiguration, andrelease of RBs. An RB refers to a service provided at L2, for datatransmission between the UE 10 and the E-UTRAN.

Referring to FIG. 3A, the RLC layer and the MAC layer are terminated atthe eNB 20 and may perform functions such as Automatic Repeat reQuest(ARQ) and Hybrid ARQ (HARQ). The PDCP layer is terminated at the eNB 20and may perform functions such as header compression, integrityprotection, and cyphering.

Referring to FIG. 3B, the RLC layer and the MAC layer are terminated atthe eNB 20 and perform the same functions as on the control plane. As inFIG. 3A, the RRC layer is terminated at the eNB 20 and may performfunctions such as broadcasting, paging, RRC connection management, RBcontrol, mobility functionality, and UE measurement reporting andcontrol. A NAS control protocol is terminated at the MME of the gateway30 and may perform functions such as SAE bearer management,authentication, LTE_IDLE mobility handling, paging transmission inLTE_IDLE state, and security control of signaling between the gatewayand the UE 10.

Three states are available to the NAS control protocol. LTE_DETACHEDstate is used in the absence of an RRC entity. LTE_IDLE state is usedwhen minimum UE information is stored and there is no RRC connection.LTE_ACTIVE state is used when an RRC state has been set. The RRC stateis divided into RRC_IDLE state and RRC_CONNECTED state.

In the RRC_IDLE state, the UE 10 performs Discontinuous Reception (DRX)configured by the NAS, using a unique ID assigned to the UE in atracking area. That is, the UE 10 may receive broadcast systeminformation and paging information by monitoring a paging signal in aspecific paging opportunity in every UE-specific DRX cycle. In theRRC_IDLE state, no RRC context is stored in the eNB.

In the RRC_CONNECTED state, the UE may transmit and/or receive datato/from the eNB using an E-UTRAN RRC connection and a context of theE-UTRAN. In addition, the UE 10 may report channel quality informationand feedback information to the eNB. The E-UTRAN is aware of a cell towhich the UE 10 belongs in the RRC_CONNECTED state. Therefore, thenetwork may transmit and/or receive data to/from the UE 10, controlmobility such as handover of the UE 10, and perform cell measurement onneighbor cells.

FIG. 4 illustrates a radio frame structure.

Referring to FIG. 4, an E-UMTS system uses a 10-ms radio frame. Oneradio frame includes 10 subframes. Each subframe is further divided intotwo successive slots, each slot being 0.5 ms in duration. A subframeincludes a plurality of symbols (e.g., Orthogonal Frequency DivisionMultiplexing (OFDM) or SC-FDMA symbols) in time by a plurality ofResource Blocks (RBs) in frequency. One RB has a plurality of symbols bya plurality of subcarriers. On DL, a part (e.g., the first symbol) of aplurality of symbols in a subframe may be used to transmit L1/L2 controlinformation.

Specifically, up to three (or four) OFDM symbols at the start of thefirst slot of a subframe are allocated as a control region to which a DLcontrol channel is allocated for transmission of L1/L2 controlinformation. The remaining OFDM symbols of the subframe are allocated asa data region to which a Physical Downlink Shared Channel (PDSCH) isallocated. DL control channels include a Physical Control FormatIndicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH),a Physical HARQ Indicator Channel (PHICH), etc. The PCFICH is located inthe first OFDM symbol of a subframe, carrying information about thenumber of OFDM symbols used for transmission of control channels in thesubframe. The PHICH delivers an HARQ ACKnowledgment/NegativeACKnowledgment (ACK/NACK) signal as a response to a UL transmission.

Control information transmitted on a PDCCH is called Downlink ControlInformation (DCI). DCI formats 0, 3, 3A, and 4 are defined for ULscheduling and DCI formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, and 2C aredefined for DL scheduling. Depending on its usage, a DCI formatselectively includes information such as a hopping flag, an RBassignment, a Modulation Coding Scheme (MCS), a Redundancy Version (RV),a New Data Indicator (NDI), a Transmit Power Control (TPC), a cyclicshift for a DeModulation Reference Signal (DM-RS), a Channel QualityInformation (CQI) request, an HARQ process number, a TransmittedPrecoding Matrix Indicator (TPMI), Precoding Matrix Indicator (PMI),etc.

The PDCCH delivers information about resource allocation and a transportformat for a Downlink Shared Channel (DL-SCH), information aboutresource allocation and a transport format for an Uplink Shared Channel(UL-SCH), paging information of a Paging Channel (PCH), systeminformation on the DL-SCH, information about resource allocation for ahigher-layer control message such as a random access responsetransmitted on a PDSCH, a set of transmission power control commands forindividual UEs of a UE group, a TPC command, Voice Over InternetProtocol (VoIP) activation indication information, etc. A plurality ofPDCCHs may be transmitted in the control region. A UE may monitor aplurality of PDCCHs. A PDCCH is transmitted in an aggregate of one ormore consecutive Control Channel Elements (CCEs). A CCE is a logicalallocation unit used to provide a PDCCH at a coding rate based on thestate of a radio channel. A CCE includes a plurality of Resource ElementGroups (REGs). The format of a PDCCH and the number of available bitsfor the PDCCH are determined according to the number of CCEs. An eNBdetermines a PDCCH format according to DCI to be transmitted to a UE andadds a Cyclic Redundancy Check (CRC) to the control information. The CRCis masked by an ID (e.g., a Radio Network Temporary Identifier (RNTI))according to the owner or usage of a PDCCH. If the PDCCH is directed toa specific UE, its CRC may be masked by a Cell-RNTI (C-RNTI) of the UE.If the PDCCH is for a paging message, the CRC of the PDCCH may be maskedby a Paging Indicator Identifier (P-RNTI). If the PDCCH carries systeminformation (particularly, a System Information Block (SIB)), its CRCmay be masked by a System Information RNTI (SI-RNTI). To indicate thatthe PDCCH carries a Random Access Response, its CRC may be masked by aRandom Access-RNTI (RA-RNTI).

FIG. 5 illustrates a structure of a UL subframe.

Referring to FIG. 5, a 1-ms subframe 500 includes two 0.5-ms slots 501.Each slot may include a different number of SC-FDMA symbols according toa Cyclic Prefix (CP) length. For example, a slot includes 7 SC-FDMAsymbols in the case of normal CP and 6 SC-FDMA symbols in the case ofextended CP. An RB 503 is a resource allocation unit defined as one slotin the time domain by 12 subcarriers in the frequency domain. The ULsubframe is divided into a data region 504 and a control region 505. Thedata region 504 includes a Physical Uplink Shared Channel (PUSCH) and isused to transmit a data signal such as voice. The control regionincludes a Physical Uplink Control Channel (PUCCH) and is used totransmit Uplink Control Information (UCI). The PUCCH includes an RB pairlocated at both ends of the data region 504 along the frequency axis andhops over a slot boundary.

The PUCCH may carry the following control information.

-   -   Scheduling Request (SR): information used to request UL-SCH        resources. The SR is transmitted in On-Off Keying (OOK).    -   HARQ ACK/NACK (A/N): a response signal to DL data. The HARQ A/N        indicates whether the DL data has been received successfully. A        1-bit A/N is transmitted as a response to a single DL codeword        and a 2-bit A/N is transmitted as a response to two DL        codewords.    -   Channel State Information (CSI): feedback information (e.g., a        Channel Quality Indicator (CQI) for a DL channel. Multiple Input        Multiple Output (MIMO)-related feedback information includes an        RI, a PMI, and a Precoding Type Indicator (PTI). The CSI        occupies 20 bits per subframe. Periodic CSI (p-CSI) is        transmitted periodically on a PUCCH according to a period/offset        configured by a higher layer, whereas aperiodic CSI (a-CSI) is        transmitted aperiodically on a PUSCH according to a command from        an eNB.

[Table 1] illustrates a mapping relationship between PUCCH formats andUCI in the LTE/LTE-A system.

TABLE 1 PUCCH format Uplink Control Information (UCI) format 1SR(Scheduling Request) (non-modulated waveform) format 1a 1-bit HARQACK/NACK (SR present/absent) format 1b 2-bit HARQ ACK/NACK (SRpresent/absent) format 2 CSI (20 coded bits) format 2 CSI and 1-bit or2-bit HARQ ACK/NACK (20 bits) (only in the case of extended CP) format2a CSI and 1-bit HARQ ACK/NACK (20 + 1 coded bits) format 2b CSI and2-bit HARQ ACK/NACK (20 + 2 coded bits) format 3 (LTE-A) HARQ ACK/NACK +SR (48 bits)

An A/N and CSI may need to be transmitted in the same subframe. If ahigher layer sets simultaneous A/N+CSI transmission as not allowed(“Simultaneous-AN-and-CAI” parameter=OFF), only the A/N is transmittedin PUCCH format 1a/1b, while the CSI transmission is dropped. On theother hand, if the higher layer sets simultaneous A/N+CSI transmissionas allowed (“Simultaneous-AN-and-CAI” parameter=ON), both the A/N andthe CQI are transmitted in PUCCH format 2/2a/2b. Specifically, in thecase of normal CP, the A/N is embedded in the second RS of each slot(e.g., the A/N is multiplied by the RS) in PUCCH format 2a/2b. In thecase of extended CP, the A/N and the CQI are encoded jointly andtransmitted in PUCCH format 2.

FIG. 6 illustrates a slot-level structure of PUCCH format 1a/1b. PUCCHformat 1 used for SR transmission is identical to PUCCH format 1a/1b instructure.

Referring to FIG. 6, 1-bit A/N information [b(0)] and 2-bit A/Ninformation [b(0)b(1)] are modulated respectively in Binary Phase ShiftKeying (BPSK) and Quadrature Phase Shift Keying (QPSK) to one A/Nmodulation symbol d0. Each bit [b(i), i=0,1] of the A/N informationindicates an HARQ response for a corresponding Transport Block (TB). Ifthe bit is 1, it indicates a positive ACK and if the bit is 0, itindicates a NACK. [Table 4] is a modulation table for PUCCH formats 1aand 1 b in the legacy LTE system.

TABLE 2 PUCCH format b(0), . . . , b(M_(bit) − I) d(0) 1a 0 1 1 −1  1b00 1 01 −j  10 j 11 −1 

PUCCH format 1a/1b is cyclically shifted (α_(cs,x)) in the frequencydomain and spread with an orthogonal code (e.g., a Walsh—Hadamard or aDiscrete Fourier Transform (DFT) code) w₀, w₁, w₂, and w₃ in the timedomain.

FIG. 7 illustrates PUCCH format 2/2a/2b.

Referring to FIG. 7, if a normal CP is configured, PUCCH format 2/2a/2bincludes five QPSK data symbols and two Reference Signal (RS) symbols ata slot level. If an extended CP is configured, an RS symbol is locatedin the fourth SC-FDMA symbol of each slot. Therefore, PUCCH format2/2a/2b may carry 10 QPSK data symbols in total. Each QPSK symbol isspread with a Cyclic Shift (CS) in the frequency domain and mapped to acorresponding SC-FDMA symbol. RSs may be multiplexed in Code DivisionMultiplexing (CDM) using a CS.

FIG. 8 illustrates a random access procedure.

Referring to FIG. 8, a UE receives random access information from an eNBby system information. Subsequently, when random access is needed, theUE transmits a Random Access Preamble (message 1) to the eNB (S810).Upon receipt of the Random Access Preamble from the UE, the eNBtransmits a Random Access Response (RAR) message (message 2) to the UE(S820). Specifically, DL scheduling information for the RAR message isCRC-masked by an RA-RNTI and transmitted on an L1/L2 control channel(PDCCH). The PDCCH masked by the RA-RNTI (hereinafter, referred to asRAR-PDCCH) is transmitted in a common search space. Upon receipt of theDL scheduling signal masked by the RA-RNTI, the UE may receive the RARmessage on a scheduled PDSCH and decode the RAR message. Then, the UEdetermines whether RAR information directed to the UE is included in theRAR message. The UE may determine whether the RAR information directedto the UE is included by checking the presence or absence of a RandomAccess preamble ID (RAID) for the preamble transmitted by the UE. TheRAR information includes a Timing Advance (TA), UL resource allocationinformation, a temporary UE ID identifying the UE (e.g., a TemporaryC-RNTI or TC-RNTI), etc. Upon receipt of the RAR response information,the UE transmits a UL message (message 3) to the eNB on a UL-SCHaccording to the radio resource allocation information included in theRAR information (S830). After receiving the UL message, the eNBtransmits a contention resolution message (message 4) to the UE (S840).

FIG. 9 illustrates an exemplary UL-DL timing relationship.

Referring to FIG. 9, a UE may start to transmit UL radio frame #i(N_(TA)+N_(TAoffset))×T_(s) before the starting point of a DL radioframe linked to UL radio frame #i. Here, 0≤N_(TA)≤20512. N_(TAoffset)=0in Frequency Division Duplex (FDD) and N_(TAoffset)=624 in Time DivisionDuplex (TDD). N_(TA) is indicated by a TA Command (TAC) and the UEadjusts the transmission timing of a UL signal (e.g., a PUCCH, a PUSCH,a Sounding Reference Signal (SRS), etc.) by (N_(TA)+N_(TAoffset))×T_(s).The UL transmission timing may be adjusted in units of 16 T_(S). T_(S)is a sampling time. A TAC set in an RAR message is 11 bits, indicating avalue ranging from 0 to 1282 and N_(TA)=TA×16. Otherwise, a TAC is 6bits, indicating a value ranging from 0 to 63 andN_(TA)=N_(TA,old)+(TA-31)×16. A TAC received in subframe #n is appliedafter subframe #n+6.

FIG. 10 illustrates an exemplary handover procedure.

Referring to FIG. 10, a UE 10 transmits a measurement report to a sourceeNB 20 (S102). The source eNB 20 transmits a handover request messagealong with a context of the UE 10 to a target eNB 30 (S104). The targeteNB 30 transmits a handover request response message to the source eNB20 (106). The handover request response message includes informationsuch as a part of a handover command message and a dedicated preambleindex for contention-free random access to a target cell. The source eNB20 transmits a handover command to the UE 10 (S108). The handovercommand includes random access information such as a new C-RNTI and adedicated preamble index to be used by the UE 10. The UE 10 performs arandom access procedure in the target cell after the handover command inorder to acquire a TA value. The random access procedure is acontention-free random access procedure in which a preamble index isreserved for the UE 10 to avoid collision. The UE 10 starts the randomaccess procedure with the target eNB 30 by transmitting a Random AccessPreamble using the dedicated preamble index (S110). The target eNB 30transmits an RAR message to the UE 10 (S112). The RAR message includes aTA and a UL resource assignment. The UE 10 transmits a handover completemessage to the target eNB 30 (S114).

FIG. 11 illustrates an example of determining PUCCH resources for A/Ntransmission. In the LTE/LTE-A system, PUCCH resources for an A/N arenot pre-allocated to each UE. Rather, a plurality of PUCCH resources aredivided for a plurality of UEs at each time point. Specifically, PUCCHresources in which a UE transmits an A/N are linked to a PDCCH carryingscheduling information for DL data or a PDCCH indicating Semi-PersistentScheduling (SPS) release. A PDCCH transmitted to a UE in a DL subframeincludes a plurality of CCEs. The UE may transmit an A/N in PUCCHresources linked to a specific CCE (e.g., the first CCE) among the CCEsof the received PDCCH. For example, if a PDCCH including CCEs #4, #5,and #6 delivers information about a PDSCH as illustrated in FIG. 11, theUE transmits An A/N on PUCCH #4 corresponding to the first CCE of thePDCCH, CCE #4.

Specifically, PUCCH resource indexes are determined in the LTE/LTE-Asystem, by the following equation.

n ⁽¹⁾ _(PUCCH) =n _(CCE) +N ⁽¹⁾ _(PUCCH)  [Equation 1]

In [Equation 1], n⁽¹⁾ _(PUCCH) represents a resource index of PUCCHformat 1a/1b for ACK/NACK/DTX transmission, N⁽¹⁾ _(PUCCH) is a valueindicated by higher-layer signaling, and n_(CCE) represents the smallestof CCE indexes used for PDCCH transmission. A CS, an Orthogonal Code(OC), and a Physical Resource Block (PRB) for PUCCH format 1a/1b areobtained from n⁽¹⁾ _(PUCCH).

Because an LTE UE cannot transmit a PUCCH and a PUSCH at the same time,the LTE UE multiplexes UCI in a PUSCH region (PUSCH piggyback) when theLTE UE needs to transmit UCI (e.g., a CQ/PMI, an HARQ-ACK, an RI, etc.)in a subframe carrying the PUSCH. An LTE-A UE may also be configured notto transmit a PUCCH and a PUSCH at the same time. In this case, if theLTE-A UE needs to transmit UCI (e.g., a CQ/PMI, an HARQ-ACK, an RI,etc.) in a subframe carrying the PUSCH, the LTE-A UE mat multiplex UCIin a PUSCH region (PUSCH piggyback).

FIG. 12 illustrates a UL A/N transmission procedure in a single-cellsituation.

Referring to FIG. 12, a UE may receive one or more DL transmissions(e.g., PDSCH signals) in M DL Subframes (SFs) (S502_0 to S502_M−1). EachPDSCH signal carries one or more (e.g., 2) TBs (or CodeWords (CWs))according to a Transmission Mode (TM). While not shown, a PDCCH signalrequiring an ACK/NACK response, for example, a PDCCH signal indicatingSPS release (shortly, referred to as an SPS release PDCCH signal) mayalso be received in steps S502_0 to S502_M−1. In the presence of a PDSCHsignal and/or an SPS release PDCCH signal in the M DL SFs, the UEtransmits an A/N in one UL SF corresponding to the M DL SFs after anoperation for A/N transmission (e.g., A/N (payload) generation, A/Nresource allocation, etc.) (S504). The A/N includes response informationto the PDSCH signals and/or the SPS release PDCCH signal received insteps S502_0 to S502_M−1. Although an A/N is transmitted basically on aPUCCH (e.g., see FIGS. 6 and 7), if a PUSCH is to be transmitted at atransmission time of the A/N, the A/N may be transmitted on the PUSCH.Various PUCCH formats listed in [Table 1] are available for A/Ntransmission. To reduce the number of A/N bits transmitted in a PUCCHformat, various methods such as A/N bundling, A/N channel selection,etc. may be used.

M is 1 in FDD, whereas M is an integer equal to or larger than 1 in TDD.An A/N is transmitted in one UL SF in response to data received in M DLSFs in TDD. This UL-DL relationship is given by a Downlink AssociationSet Index (DASI).

[Table 3] lists DASIs (K::{k₀,k₁, . . . k_(M−1)}) defined in theLTE/LTE-A system. If a PDSCH and/or a SPS release PDCCH is transmittedin SF (n−k) (k∈K), a UE transmits a related ACK/NACK in SF n.

TABLE 3 UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 —— 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, 4, 6— — 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 11 6, 5, 4, 7 — —— — — — 5 — — 13, 12, 9, 8, 7, 5, 4, 11, 6 — — — — — — — 6 — — 7 7 5 — —7 7 —

In TDD, the UE should transmit an A/N signal in one UL SF in response toreception of one or more DL transmissions (e.g., PDSCHs) in M DL SFs. AnA/N is transmitted in one UL SF in response to a plurality of DL SFs inthe following manners.

1) A/N bundling: A/N bits for a plurality of data units (e.g., PDSCHs,SPS release PDCCHs, etc.) are combined by a logic operation (e.g.,logic-AND operation). For example, if all of the data units are decodedsuccessfully, a receiver (e.g., a UE) transmits an ACK signal. On theother hand, if decoding (or detection) of at least one of the data unitsis failed, the receiver transmits a NACK signal or no signal.

2) Channel selection: upon receipt of a plurality of data units (e.g.,PDSCHs, SPS release PDCCHs, etc.), a UE occupies a plurality of PUCCHresources for A/N transmission. An A/N response to the plurality of dataunits is identified by a combination of PUCCH resources used for actualA/N transmission and A/N contents (e.g., bit values or QPSK symbolvalues). The channel selection scheme is also called an A/N selectionscheme or a PUCCH selection scheme.

FIG. 13 illustrates an exemplary Carrier Aggregation (CA) system. AnLTE-A system uses CA or bandwidth aggregation by aggregating a pluralityof UL/DL frequency blocks to a broader frequency band. Each frequencyblock is transmitted in a Component Carrier (CC). The CC may beunderstood as a carrier frequency (center carrier or center frequency)for the frequency block.

Referring to FIG. 13, a broader UL/DL bandwidth may be supported byaggregating a plurality of UL/DL CCs. The CCs may be contiguous ornon-contiguous in the frequency domain. The bandwidth of each CC may bedetermined independently. Asymmetric CA is available, in which thenumber of UL CCs is different from that of DL CCs. For example, if thereare two DL CCs and one UL CC, the DL CCs and the UL CC may be configured2:1. A DL CC/UL CC link may be configured statically or semi-staticallyin a system. Even though a total system band includes N CCs, a frequencyband that a specific UE may monitor/receiver may be limited to L (<N)CCs. Various parameters for CA may be configured cell-specifically, UEgroup-specifically, or UE-specifically. Control information may beconfigured to be transmitted and received only in a specific CC. Thisspecific CC may be referred to as a Primary CC (PCC, or anchor CC) andthe other CCs may be referred to as Secondary CCs (SCCs).

The LTE-A system adopts the concept of cell to manage radio resources. Acell is defined as a combination of DL resources and UL resources,although the UL resources are not mandatory. Accordingly, a cell may beconfigured with DL resources alone or both DL and UL resources. If CA issupported, linkage between the carrier frequency of DL resources (or DLCCs) and the carrier frequency of UL resources (or UL CCs) may beindicated by system information. A cell operating in a primary frequency(or PCC) may be referred to as a Primary Cell (PCell) and a celloperating in secondary frequency (or SCC) may be referred to as aSecondary Cell (SCell). The PCell is used for a UE to perform an initialconnection establishment procedure or a connection reconfigurationprocedure. The PCell may be a cell indicated during a handoverprocedure. The SCell may be configured after an RRC connection isestablished and used to additional radio resources. The PCell and theSCell may be collectively called serving cells. Accordingly, For a UE inRRC_CONNECTED state, if CA is not configured for the UE or the UE doesnot support CA, a single serving cell including only a PCell exists forthe UE. On the contrary, if the UE is in RRC_CONNECTED state and CA isconfigured for the UE, one or more serving cells may exist for the UE,including a PCell and one or more SCells. For CA, the network mayconfigure one or more SCells for a UE supporting CA in addition to aPCell configured initially during a connection establishment procedure,after an initial security activation procedure starts.

If cross-carrier scheduling (or cross-CC scheduling) is used, a PDCCHfor DL allocation may be transmitted in DL CC #0 and a PDSCHcorresponding to the PDCCH may be transmitted in DL CC #2. For cross-CCscheduling, the introduction of a Carrier Indicator Field (CIF) may beconsidered. The presence or absence of a CIF in a PDCCH may beconfigured semi-statically or UE-specifically (or UE group-specifically)by higher layer signaling (e.g., RRC signaling). The baseline of PDCCHtransmission is summarized as follows.

-   -   CIF disabled: A PDCCH in a DL CC allocates PDSCH resources of        the same DL CC or PUSCH resources of one UL CC linked to the DL        CC.    -   CIF enabled: A PDCCH in a DL CC may allocate PDSCH or PUSCH        resources of a specific DL/UL CC from among a plurality of        aggregated DL/UL CCs, using a CIF.

In the presence of a CIF, an eNB may allocate a DL CC set for PDCCHmonitoring in order to reduce Blind Decoding (BD) complexity of a UE.The PDCCH monitoring DL CC set is a part of total DL CCs, including oneor more DL CCs and the UE detects/decodes a PDCCH only in the DL CCs. Inother words, when the eNB schedules a PDSCH/PUSCH for the UE, the PDCCHtransmits a PDCCH only in the PDCCH monitoring DL CC set. The PDCCHmonitoring DL CC set may be configured UE-specifically, UEgroup-specifically, or cell-specifically. The term “PDCCH monitoring DLCC” may be replaced with an equivalent term such as monitoring carrier,monitoring cell, etc. Further, aggregated CCs for a UE may beinterchangeably used with serving CCs, serving carriers, serving cells,etc.

FIG. 14 illustrates an exemplary scheduling in the case where aplurality of carriers are aggregated. In the example of FIG. 14, threeDL CCs are aggregated and DL CC A is configured as a PDCCH monitoring DLCC. DL CC A, DL CC B, and DL CC C may be referred to as serving CCs,serving carriers, serving cells, etc. If a CIF is disabled, each DL CCmay carry a PDCCH that schedules its PDSCH without a CIF according to anLTE PDCCH rule. On the contrary, if the CIF is enabled, DL CC A(monitoring DL CC) may carry a PDCCH that schedules a PDSCH of anotherCC as well as a PDCCH that schedules a PDSCH of DL CC A, using the CIF.In this case, DL CC B and DL CC C that have not been configured asmonitoring DL CCs do not carry a PDCCH.

FIG. 15 illustrates an example of allocating DL physical channels to asubframe.

Referring to FIG. 15, a legacy LTE/LTE-A PDCCH (for the convenience,referred to as a legacy PDCCH or an L-PDCCH) may be allocated to thecontrol region of a subframe (refer to FIG. 4). In FIG. 15, an L-PDCCHregion is a region available for allocation of a legacy PDCCH. A PDCCHmay be additionally allocated to the data region of the subframe (e.g.,a resource region for a PDSCH). The PDCCH allocated to the data regionis referred to as an Enhanced PDCCH (E-PDCCH). As illustrated in FIG.15, scheduling limitations imposed by limited control channel region ofthe L-PDCCH region may be mitigated by securing additional controlchannel resources through the E-PDCCH. Like the L-PDCCH, the E-PDCCHdelivers DCI. For example, the E PDCCH may carry DL schedulinginformation and UL scheduling information. For example, a UE may receivean E-PDCCH and receive data/control information on a PDSCH correspondingto the E-PDCCH. Further, the UE may receive an E-PDCCH and transmitdata/control information on a PUSCH corresponding to the E-PDCCH. AnE-PDCCH/PDSCH may start from the first OFDM symbol of a subframedepending on a cell type.

FIG. 16 illustrates a MAC PDU. MAC PDUs are transmitted on a DL-SCH anda UL-SCH.

Referring to FIG. 16, the MAC PDU includes a MAC header, zero or moreMAC Service Data Units (SDUs), and zero or more MAC Control Elements(CEs). MAC PDU subheaders are arranged in the same order as theircorresponding MAC SDUs and MAC CEs. A MAC CE is located before a MACSDU. The MAC CE carriers various types of MAC control information. Forexample, the MAC CE includes SCell activation/deactivation information,TAC information, Buffer Status Report (BSR) information, and PowerHeadroom Report (PHR) information.

FIG. 17 illustrates a SCell activation/deactivation MAC CE. An eNB mayactivate or deactivate total individual SCells aggregated for a UE usinga SCell activation/deactivation MAC CE. On the contrary, a PCell isalways activated.

Referring to FIG. 17, the activation/deactivation MAC CE is identifiedby a MAC PDU having a Logical Channel Identifier (LCID) indicatingactivation/deactivation (e.g., LCID=11011). The activation/deactivationMAC CE is one octet, including seven C-fields and one R-field.

-   -   C_(i): indicates an active/inactive state of a SCell having        SCellIndex i. In the absence of a SCell having SCellIndex I, a        UE ignores the C_(i) field. If the C_(i) field indicates        activation, it is set to 1 and if C_(i) field indicates        deactivation, it is set to 0.    -   R: a reserved bit. It is set to 0.

FIG. 18 illustrates a TAC MAC CE. An eNB may adjust a UL timing on aTiming Advance Group (TAG) basis for all TAGS configured for a UE usinga TAC MAC CE. The TAC MAC CE includes a TAG Identity (TAG ID) field anda TAC field.

-   -   TAG: indicates a TAG. If the TAG includes a PCell, the TAG ID=0.    -   TAC: indicates a timing adjustment amount to be applied to a UE.        The TAC is 6 bits indicating a value ranging from 0 to 63. For        details, refer to FIG. 9.

FIG. 19 illustrates a Power Headroom (PH) MAC CE, particularly, anextended PH MAC CE. The PH MAC CE may indicate a PH for all aggregatedcells to a UE. The PH MAC CE includes the following fields.

-   -   C_(i): indicates whether a PH field exists for a SCell having        SCellIndex i. If a PH field for a SCell having SCellIndex i is        reported, the C_(i) field is set to 1 and otherwise, the C_(i)        field is set to 0.    -   R: a reserved bit. It is set to 0.    -   V: indicates whether a PH value is based on actual transmission        or a reference format.    -   PH: indicates a PH level.    -   P: indicates whether a backoff is applied for power management        of a UE.    -   P_(CMAX,c): provides information about maximum power per cell,        used to calculate the value of a previously positioned PH field.

Embodiments: Signaling in Inter-Site CA

The LTE-A system supports aggregation of a plurality of cells (i.e., CA)and considers management of all of a plurality of cells aggregated forone UE by one eNB (intra-site CA). In intra-site CA, since one eNBmanages all cells, signaling related to RRC configurations/reports andMAC commands/messages may be performed in any of the cells. For example,signaling related to an operation for adding or releasing a specificSCell to or from a CA cell set, an operation for changing a TransmissionMode (TA) of a specific cell, an operation for performing Radio ResourceManagement (RRM) measurement reporting related to a specific cell, etc.may be performed in any cell of a CA cell set. In another example,signaling related to an operation for activating/deactivating a specificSCell, an operation for transmitting a Buffer Status Report (BSR) for ULbuffer management, etc. may be performed in any cell of a CA cell set.In a further example, a per-cell Power Headroom Report (PHR) for ULpower control, a per-TAG TAC for UL synchronization control, etc. may besignaled in any cell of a CA cell set.

In future systems after LTE-A, a plurality of cells having smallcoverage (e.g., micro cells) may be deployed within a cell having largercoverage (e.g., a macro cell), for traffic optimization. For example, amacro cell and a micro cell may be aggregated for one UE. The macro cellmay be used mainly for mobility management (e.g., PCell) and the microcell may be used mainly for boosting throughput (e.g., SCell). In thiscase, the cells aggregated for the UE may have different coverage andmay be managed by different eNBs (or nodes corresponding to the eNBs(e.g., relays)) geographically apart from each other (inter-site CA).

FIG. 20 illustrates an exemplary inter-site CA. Referring to FIG. 20, aneNB managing a PCell (e.g., CC1) may be responsible for controlling andmanaging radio resources (e.g., all RRC functions and partial MACfunctions) for a UE and each eNB managing a cell (i.e., CC1 or CC2) maybe responsible for data scheduling and feedback (e.g., all PHY functionsand main MAC functions) for the cell. Accordingly, information/dataneeds to be exchanged/transmitted between cells (i.e., eNBs). Inconsideration of legacy signaling, information/data may beexchanged/transmitted between cells (i.e., eNBs) through a backhaul (BH)(e.g., via a wired X2 interface or a radio backhaul link) in inter-siteCA. However, if the legacy signaling is still used, cell managementstability, resource control efficiency, data transmission adaptability,etc. may be significantly reduced due to latency involved in signalingbetween eNBs.

For example, an inter-site CA situation may be assumed, in which a PCell(e.g., CC1) and a SCell (e.g., CC2) aggregated for one UE are managed byeNB-1 and eNB-2 respectively, as illustrated in FIG. 20. It is alsoassumed that the eNB managing the PCell (i.e., eNB-1) manages/controlsRRC functions related to the UE. If an RRM measurement (e.g., ReferenceSignal Received Power (RSRP) or Reference Signal Received Quality(RSRQ)) report related to the SCell is transmitted in the SCell (e.g.,via a PUSCH), not the PCell, eNB-2 may have to transmit the RRMmeasurement report to eNB-1 through the BH. If eNB-1, for example,transmits an RRC reconfiguration command requesting release of the SCellfrom a CA cell set to the UE in the PCell (e.g., via a PDSCH), the UEmay transmit a confirmation response for the RRC reconfiguration commandin the SCell (e.g., via a PUSCH), not the PCell. In this case, eNB-2 mayhave to transmit the confirmation response to eNB-1 through the BH.Thus, the inter-site CA may cause a great latency during signalingbetween the cells (i.e., the eNBs). As a result, a mismatch in CA cellset interpretation may occur between an eNB and a UE andstable/efficient management and control of cell resources may not befacilitated.

In another example, per-cell PHRs of all cells may be transmitted in thePCell (e.g., via a PUSCH) in the above inter-site CA situation. In thiscase, eNB-1 (managing the PCell) may have to transmit all PHRs or a PHRcorresponding to the SCell to eNB-2 (managing the SCell) through the BH.On the contrary, if the per-cell PHRs of all cells are transmitted inthe SCell, eNB-2 may have to transmit all PHRs or a PHR corresponding tothe PCell to eNB-1 through the BH. As described before, stable/efficientUL power control and adaptive UL data scheduling/transmission based onthe UL power control may not be easy due to latency involved insignaling between the eNBs.

To avert the above problem, it is proposed that a path for specificsignaling (e.g., RRC, MAC, DCI, and UCI) related to a specific cell(e.g., a cell or cell group that may perform a transmission/receptionoperation regarding signaling) is configured in an inter-site CAsituation or its similar situation. For example, a path (e.g., a cell orcell group) for performing a signal/channel transmission and/orreception operation accompanying specific signaling related to aspecific cell may be configured. In this case, a UE may operate,considering that a signal/channel accompanying the specific signalingrelated to the specific cell may be transmitted and/or received only inthe configured path. For example, reception/detection/monitoring and/ortransmission/encoding of the signal/channel accompanying the specificsignaling related to the specific cell may be performed only in theconfigured path, not in any other path. According to the presentinvention, a specific cell covers a cell or a cell group. For thispurpose, a plurality of aggregated cells may be divided into one or morecell groups. Each cell group includes one or more cells. For theconvenience, a cell group including a PCell is referred to as a PCellgroup and a cell group including only SCells is referred to as a SCellgroup. There may be one PCell group and zero or more SCell groups.Unless otherwise mentioned herein, a PDCCH may cover both an L-PDCCH andan E-PDCCH.

A signaling method/path proposed by the present invention may beperformed only in inter-site CA or a similar CA situation. In otherwords, not the signaling method/path proposed by the present inventionbut a conventional signaling method/path may be applied to an intra-CAsituation. A CA mode (i.e., inter-site CA or intra-site CA) may beconsidered to configure a signaling method/path on the part of an eNB,whereas knowledge of a used signaling method/path is sufficient on thepart of a UE. Therefore, the eNB may transmit only indicationinformation indicating the applied signaling method/path to the UE,without indicating a CA mode. If the UE can determine the CA mode duringCA configuration, the UE may determine the signaling method/path appliedto the UE based on the CA mode. Accordingly, the eNB may not transmitthe indication information indicating the signaling method/path to theUE.

Signaling for which a path needs to be configured may include thefollowings according to the present invention.

-   -   command/response transmitted during RRC        configuration/reconfiguration (e.g., SCell        allocation/deallocation, per-cell TM configuration, and per-cell        CSI feedback mode/SRS parameter configuration)    -   Radio Link Monitoring (RLM) (e.g., Radio Link Failure (RLF)) and        RRM measurement (e.g., RSRP or RSRQ)-related        configuration/report    -   Handover (HO)-related command/response    -   SCell MAC activation/deactivation (i.e. SCell Act/De) message    -   PHR, BSR, and TAC    -   DCI (e.g., DL/UL grant) and Scheduling Request (SR)    -   Periodic CSI (p-CSI) report and aperiodic CSI (a-CSI)        request/report    -   ACK/NACK (A/N) feedback in response to DL data reception    -   Random Access Response (RAR) and PDCCH that schedules a PDSCH        carrying the RAR (hereinafter, referred to as RAR PDCCH)

For example, a path for signaling involved in an RRC reconfigurationoperation for additionally allocating/deallocation a specific cellto/from a CA cell set and an RRM measurement (e.g., RSRP or RSRQ) reportrelated to the specific cell may be configured as a PCell group. In thiscase, the signaling involved in the RRC reconfiguration/measurementreport related to the specific cell may be transmitted/received onlythrough the PCell group (a PDSCH/PUSCH in any cell belonging to thePCell group). Further, a path in which a per-cell PHR may be signaledfor UL power control of a specific cell group (or all cells of the cellgroup) may be configured as the specific cell group. That is, a PHR forthe specific cell group may be transmitted only through the specificcell group (on a PUSCH of any cell belonging to the specific cellgroup).

FIG. 21 illustrates an exemplary signaling method according to anembodiment of the present invention. Referring to FIG. 21, a path inwhich signaling related to a specific cell is performed in the situationillustrated in FIG. 20 may be limited to CC1 (group) and CC2 (group)according to the type of the signaling. Specifically, the presentinvention provides the following path configuration methods according tosignaling types.

Case #1

-   -   Signaling type: command/response transmitted during RRC        configuration/reconfiguration (e.g., SCell        allocation/deallocation, per-cell TM configuration, and per-cell        CSI feedback mode/SRS parameter configuration), RLM (e.g., RLF)        and RRM measurement (e.g., RSRP or RSRQ)-related        configuration/report, and HO-related command/response    -   Signaling for a specific cell (or a specific cell group): the        path may be configured as a PCell group.

Case #2

-   -   Signaling type: SCell MAC activation/deactivation message (i.e.,        SCell Act/De), PHRs, BSR, TACs, DCI (e.g., DL/UL grant), and        a-CSI request/report    -   Signaling for a specific cell (or a specific cell group): the        path may be configured as a cell group to which the specific        cell belongs (or the specific cell group). In this case, the        following constraints may be imposed on the signaling.    -   An activation/deactivation cell list in the SCell Act/De message        may include only SCells belonging to the specific cell group.    -   The PHRs may include only the PHR of each cell of the specific        cell group. Further, a PHR transmission period may be set        independently on a cell group basis.    -   The BSR may report only the UL buffer state of the specific cell        group (or all cells of the specific cell group).    -   The TACs may include only per-TAG TACs of the specific cell        group. Further, cells of different cell groups may not belong to        the same TAG.    -   The DCI may be scheduling/control information (e.g., a DL/UL        grant) only for a cell(s) of the specific cell group. Further,        cross-CC scheduling may not be allowed between cells of        different cell groups (i.e., DCI (e.g., a DL/UL grant) for a        cell of the specific cell group may not be transmitted from        cells belonging to other cell groups).    -   The a-CSI request/report may be only for a cell(s) of the        specific cell group. Further, an a-CSI reporting cell set        indicated by RRC signaling may be configured independently for        each cell group (i.e., an a-CSI reporting cell set applied to an        a-CSI request/report of the specific cell group may include only        a cell(s) of the specific cell group). In addition, the number        of bits of an a-CSI request field in DCI may be determined        independently according to the number of cells belonging to a        cell group (scheduled by the DCI) (e.g., the number of bits in        the a-CSI request field is 1 bit for one cell and 2 bits for two        or more cells). In another method, for every SCell group or a        specific SCell group, the a-CSI request field of DCI (scheduling        the SCell group) may be fixed to one bit and only each cell of        the SCell group may be allowed for a-CSI reporting, in order to        reduce RRC signaling overhead.

Case #3

-   -   Signaling type: ACK/NACK (A/N) for DL data, SR, and p-CSI report    -   Signaling for cell of PCell group: if signaling information is        transmitted on a PUCCH, the path may be configured as a PCell.        If signaling information is transmitted on a PUSCH (i.e., the        signaling information is piggybacked to the PUSCH, that is,        multiplexed with UL data), the path may be configured as the        PCell group (i.e. a PUSCH transmission cell of the PCell group).    -   Signaling for specific SCell of SCell group: if signaling        information is transmitted on a PUCCH, the path may be        configured as a specific SCell or a specific selected SCell of        the SCell group (e.g., a cell or one of cells configured to        transmit a PDCCH (e.g., DL/UL grant) or perform (DL/UL data)        scheduling in the SCell group may be determined as the specific        selected SCell (by signaling), or a cell having a specific        (e.g., the smallest) cell index or a specific (e.g., the        broadest) system bandwidth among the corresponding cell(s)        (herein, among a cell(s) for which UL resources/carriers have        been defined may be automatically determined as the specific        selected SCell). If signaling information is transmitted on a        PUSCH (i.e., the signaling information is piggybacked to the        PUSCH, that is, multiplexed with UL data), the path may be        configured as the SCell group to which the specific SCell        belongs. In this case, the following constraints may be imposed        on the signaling.    -   An A/N transmitted on a PUCCH of a SCell in a SCell group may        include only individual A/N responses for DL data receptions in        the SCell. Because unlike a PCell, a SCell may be        activated/deactivated, if a PUCCH is transmitted in a        predetermined SCell of the SCell group, the predetermined SCell        may be inactive at a time when an A/N is to be transmitted.        Accordingly, it may be preferred (in the case of a SCell group)        that an A/N for a SCell in which DL data has been received is        transmitted only in the SCell. In another method, in order to        reduce use of explicit PUCCH resources and the overhead of RRC        signaling related to allocation of the PUCCH resources and        increase the use efficiency of implicit PUCCH resources, it may        be defined/regulated that an A/N for DL data reception in a        specific SCell (of a SCell group) is transmitted in a cell in        which a DL grant PDCCH scheduling the DL data has been        transmitted.    -   An A/N piggybacked to a PUSCH in a specific SCell of a SCell        group may include A/N responses for DL data receptions in all        cells of the SCell group.    -   An SR transmitted on a PUCCH of a specific SCell in a SCell        group may be a UL SR only for the SCell group (or all cells of        the SCell group).    -   p-CSI transmitted on a PUCCH in a specific SCell of a SCell        group may be limited to p-CSI for a specific SCell. Further,        p-CSI piggybacked to a PUSCH in a SCell of a SCell group may        include only p-CSI of one or more cells of the SCell group.

Case #4

-   -   Signaling type: RAR and RAR-PDCCH    -   Signaling for Physical Random Access Channel (PRACH)        transmission in cell of PCell group: a RAR path may be        configured as a PCell and a RAR-PDCCH path may be configured as        a Common Search Space (CSS) in the PCell.    -   Signaling for PRACH transmission in specific SCell of SCell        group: a RAR path may be configured as the specific SCell or a        specific selected SCell of the SCell group. A RAR-PDCCH path may        be configured as a CSS in the specific SCell or the specific        selected SCell of the SCell group (as described before, for        example, a cell or one of cells configured to transmit PDCCH        (e.g., DL/UL grant) transmission or perform (DL/UL data)        scheduling in the SCell group may be configured as the specific        selected SCell (by signaling), or a cell having a specific        (e.g., the smallest) cell index or a specific (e.g., the        broadest) system bandwidth among the corresponding cell(s)        (herein, among a cell(s) for which UL resources/carrier has been        defined may be automatically determined as the specific selected        SCell).

Compared to the above example, case #1 may be applied to SCell Act/De.In this case, paths in which MAC signaling related toactivation/deactivation of a specific SCell may all be configured as aPCell group.

To avoid simultaneous transmission of a plurality of PUCCHs, a PUCCHtransmitted in a SCell in case #3 may be replaced with PUSCH resources(hereinafter, referred to as UCI-PUSCH resources) or a DemodulationReference Signal (DMRS) for PUSCH demodulation (hereinafter, referred toas UCI-DMRS). The UCI-PUSCH resources may be dedicated to UCItransmission (not UL data transmission). The UCI-PUSCH resources mayinclude PUSCH resources configured with one subframe (hereinafter,referred to as normal PUSCH resources), PUSCH resources configured withone slot (hereinafter, referred to as slot PUSCH resources), or PUSCHresources configured with a small number of SC-FDMA symbols(hereinafter, referred to as shortened PUSCH resources). The shortenedPUSCH resources may include N (e.g., N=2 or 3)SC-FDMA symbols per slot.In this case, one or two SC-FDMA symbols may be used as DMRStransmission symbols and the other one or two SC-FDMA symbols may beused as UCI transmission symbols, in each slot. Accordingly, a pluralityof shortened PUSCH resources may be multiplexed (in Time DivisionMultiplexing (TDM)) in one UL RB (pair).

Thus, the UCI-PUSCH resources may be identified by a UL RB index, a slotindex (in a UL RB), an SC-FDMA symbol index, a CS and/or OCC(combination) index of a DMRS, etc. UCI-PUSCH resources may be allocatedindividually for each of an A/N, an SR, and p-CSI, one common UCI-PUSCHresource may be allocated to all of the UCI, or one UCI-PUSCH resourcemay be allocated to two pieces of UCI (e.g., the A/N and the SR), withone UCI-PUSCH resource allocated to the other one piece of UCI (e.g.,the p-CSI), which should not be construed as limiting the presentinvention. The UCI-PUSCH resources may be allocated preliminarily by RRCsignaling. Further, a plurality of UCI-PUSCH resources may be allocatedpreliminarily by RRC signaling and then a specific UCI-PUSCH resourcemay be indicated from among the plurality of UCI-PUSCH resources by a DLgrant PDCCH. Specifically, the UCI-PUSCH resource may be indicated by aspecific field (e.g., an A/N Resource Indicator (ARI) field) of the DLgrant PDCCH. Further, a UCI-PUSCH resource linked to a specific DL RBindex (e.g., the smallest DL RB index) occupied by DL data (with linkageset/configured between DL RB resources and UCI-PUSCH resources). Inaddition, a UCI-PUSCH resource linked to a specific CCE index (e.g., thesmallest CCE index) of a PDCCH scheduling DL data may be allocated (withlinkage set/configured between CCE resources and UCI-PUSCH resources).

UCI-DMRS resources may include M (M=1, 2, or 3)SC-FDMA symbols in eachslot. Unlike shortened PUSCH resources, the M symbols of the UCI-DMRSresources may all be used as DMRS transmission symbols only. UCI-DMRSresources including one slot may also be used for UCI transmission andthus a plurality of UCI-DMRS resources may be multiplexed (in TDM) inone UL RB (pair). Methods for transmitting UCI in UCI-DMRS resources mayinclude 1) selection/transmission of different UCI-DMRS resourcesaccording to a UCI value (e.g., an ACK or NACK or a positive or negativeSR) (among a plurality of UCI-DMRS resources), 2) transmission ofmodulation (e.g., BPSK or QPSK) DMRS symbols in UCI-DMRS resourcesaccording to a UCI value, and/or methods 1) and 2) in combination.According to method 2), a specific DMRS symbol (e.g., the first DMRSsymbol) in the UCI-DMRS resources may be fixed without modulation (thus(similarly to legacy PUCCH format 2a/2b in which a CQI and an A/N aretransmitted simultaneously by differential DMRS modulation), a receiver(an eNB) may receive UCI by detecting a signal difference (e.g., phasedifference) between the fixed DMRS symbol and a modulated DMRS symbol).

The UCI-DMRS resources may be identified by a UL RB index, a slot index(in a UL RB), an SC-FDMA symbol index, a CS and/or OCC (combination)index, etc. Further, separate or common UCI-DMRS resources may beallocated only to an A/N and an SR and UCI-PUSCH resources may beallocated to p-CSI. The UCI-DMRS resources may be allocatedpreliminarily by RRC signaling. Or while a plurality of UCI-DMRSresources have already been allocated by RRC signaling, a UCI-DMRSresource to be used may be signaled by a PDCCH (e.g., an ARI field ofthe PDCCH). Further, a UCI-DMRS resource linked to a specific DL RBindex (e.g., the smallest DL RB index) occupied by DL data or a specificCCE index (e.g., the smallest CCE index) of a PDCCH scheduling DL datamay be allocated (with linkage set/configured between DL RB resources orCCE resources and UCI-DMRS resources).

The signaling path configuration method of the present invention is notlimited to the afore-mentioned signaling types. For example, thesignaling path configuration method of the present invention is alsoapplicable to other signaling related to RRC/MAC/DCI/UCI, etc. Forexample, case #1, case #2, and case #3 may be applied to RRC signaling,MAC signaling, and DCI/UCI-related signaling, respectively.

Different cell groups may be set/configured according to signaling orsignaling sets (that is, an independent cell group may be set/configuredfor each signaling or signaling set). Further, when different cellshaving different frame types (e.g., FDD and TDD frame types) ordifferent CP lengths (e.g., normal CP and extended CP) are basicallyset/configured to belong to different cell groups, the signaling pathconfiguration method of the present invention may be implemented. Inthis case, once a cell group is set (without an additional signalingpath configuration operation), the signaling path configuration method(case #1, case #2, case #3, and case #4) of the present invention may beautomatically applied.

On the other hand, a method for, for each cell, setting a cell forperforming signaling (signal/channel transmission and/or receptionaccompanying the signaling) related/for/corresponding to the cell(without setting/configuring a cell group) may be considered. Forexample, the following per-cell path configuration may be possible forthe afore-described signaling.

-   -   RRC configuration/reconfiguration    -   For each cell, a cell that will perform command/response        transmission accompanying RRC configuration/reconfiguration        (such as SCell allocation/deallocation, per-cell TM        configuration, per-cell CSI feedback mode/SRS parameter        configuration, etc.) for the cell may be configured.    -   RRM measurement    -   For each cell, a cell that will perform RRM measurement (such as        RSRP or RSRQ)-related configuration/report transmission for the        cell may be configured.    -   RLM/HO    -   A cell that will perform RLM-related configuration/report and HO        command/response transmission may be configured.    -   SCell activation/deactivation    -   For each cell, a cell that will perform activation/deactivation        message transmission for the cell may be configured.    -   PHR/BSR/TAC    -   For each cell, a cell that will perform PHR, BSR, and TAC        transmission for the cell may be configured.    -   DCI    -   For each cell, a cell that will perform DCI (such as DL/UL        grant) transmission for the cell may be configured.    -   SR    -   For each cell, a cell that will perform SR transmission for the        cell may be configured.    -   p-CSI report    -   For each cell, a cell that will perform p-CSI report        transmission for the cell may be configured.    -   a-CSI request/report    -   For each cell, a cell that will perform a-CSI request/report        transmission for the cell may be configured.    -   ACK/NACK    -   For each cell, a cell that will perform A/N feedback        transmission for DL data received in the cell may be configured.    -   RAR and RAR-PDCCH    -   For each cell, a cell that will perform RAR and RAR-PDCCH        transmission for a PRACH received in the cell may be configured.

In another method, in the case of an HARQ-ACK for DL data, informationabout a cell and/or a subframe for HARQ-ACK transmission may beindicated by DL grant DCI that schedules DL data in consideration ofcoordination between cells (eNBs) regarding PUCCH and/or UCItransmission. Specifically, (information about) a plurality of (e.g., 2)cells/subframes are predefined/predetermined and then a cell/subframefor performing HARQ-ACK transmission for DL data may be indicated fromamong the plurality of cells/subframes by DL grant DCI. Further, aplurality of cells may be defined/determined as a PCell and a cell inwhich DL grant DCI (or DL data) has been transmitted. The plurality ofsubframes may be defined/determined as an HARQ-ACK transmission subframe(i.e., an original A/N SF) corresponding to a DL grant DCI (or DL data)reception subframe (determined based on a legacy HARQ-ACK timing definedin a legacy (e.g., Rel-10/11) FDD/TDD system) and the earliest UL SF(defined according to an HARQ-ACK timing) after the correspondingoriginal A/N SF.

Similarly, in the case of a PHICH for UL data, information about a celland/or a subframe for PHICH transmission may be indicated by DL grantDCI that schedules UL data in consideration of coordination betweencells (eNBs) regarding DL control resource transmission. Specifically,(information about) a plurality of (e.g., 2) cells/subframes arepredefined/predetermined and then a cell/subframe for performing PHICHtransmission for UL data may be indicated from among the plurality ofcells/subframes by UL grant DCI. Further, a plurality of cells may bedefined/determined as a PCell and a cell in which UL grant DCI (or ULdata) has been transmitted. The plurality of subframes may bedefined/determined as a PHICH transmission subframe (i.e., an originalPHICH SF) corresponding to a UL grant DCI (or UL data) receptionsubframe (determined based on a legacy PHICH timing defined in a legacy(e.g., Rel-10/11) FDD/TDD system) and the earliest DL (or special) SF(defined according to a PHICH timing) after the corresponding originalPHICH SF.

A backhaul link established for the purpose of exchanging/transmitting(UE-related) information/data between cells aggregated for one UE(sites/eNBs managing/controlling the cells), including an inter-site CA(or inter-eNB CA) situation, may be configured as a non-ideal backhaulinvolving a great latency. If the cells (the sites/eNBsmanaging/controlling the cells) exchange/transmit all information/datadirectly only through the backhaul link in the non-ideal backhaul-basedCA situation, the backhaul link may experience a great load/latency. Tomitigate the load/latency, it is proposed that specific/some cellinformation is exchanged/transmitted between cells through a UE, takinginto account the load/latency of the backhaul link and the radio channelstate of the UE. In other words, the backhaul link between cells(sites/eNBs) may be replaced with a radio link between UEs.Specifically, information exchange/transmission between cells aggregatedfor a UE may be performed via a UE-cell radio link as follows. For theconvenience, it is assumed that information related to cell 1 istransmitted to cell 2 through a UE in the case where cell 1 (e.g., CC1)and cell 2 (e.g., CC2) are aggregated for the UE, as illustrated in FIG.21.

Alt 1: Cell 1 Command

-   -   Cell 1 may command/indicate transmission/reporting of specific        information related to cell 1 to cell 2 to the UE (by a specific        DL channel/signal transmitted in cell 1).    -   The UE may transmit/report the specific information related to        cell 1 according to the command/indication of cell 1 (by a        specific UL channel/signal transmitted in cell 2).

Alt 2: UE Report

-   -   The UE may transmit/report specific information related to cell        1 directly to cell 2 at a specific time point or at every        specific period (by a specific UL channel/signal transmitted in        cell 2).    -   The specific time point may be a time point when the specific        information related to cell 1 is reconfigured/changed (or an        appropriate time after the reconfiguration/change time).    -   The specific period may be indicated by L1/L2/RRC signaling in        cell 1 or cell 2.

Alt 3: Cell 2 Request

-   -   Cell 2 may request/indicate transmission/reporting of specific        information related to cell 1 to the UE (by a specific DL        channel/signal transmitted in cell 2).    -   The UE may transmit/report the specific information related to        cell 1 according to the request/indication of cell 2 (by a        specific UL channel/signal transmitted in cell 2).

Specific cell-related information to which the proposed method forsignaling information between cells is applied may include at least a TMconfigured for a corresponding cell, a CSI feedback mode, a SRS-relatedparameter, an active/inactive state of the corresponding cell, a TAapplied to the corresponding cell, etc. Specifically in Alt 1, cell 1may command/indicate to a UE transmission/reporting of SRS-relatedparameter information configured in cell 1 (i.e., configured in cell 1for the UE) to cell 2. Accordingly, the UE may transmit/report theSRS-related parameter information configured in cell 1 to cell 2. In Alt2, the UE may transmit/report TA information applied to cell 1 directlyto cell 2 at a time of reconfiguring/changing the TA information appliedto cell 1 (i.e., the TA information applied to the UE in cell 1) (or anappropriate time point after the reconfiguration/change time). In Alt 3,cell 2 may request/indicate to the UE transmission/reporting ofinformation about an active/inactive state about cell 1 (i.e.,active/inactive state information applied to cell 1 for the UE).Accordingly, the UE may transmit/report the active/inactive stateinformation about cell 1 to cell 2.

In non-ideal backhaul-based inter-site CA (or inter-eNB CA), [PCell,SCell]=[cell 1, cell 2] may be configured for UE 1, whereas [PCell,SCell]=[cell 2, cell 1] may be configured for UE 2. Further, UE 3 mayperform communication (i.e., signal/channel transmission/reception) onlythrough one cell (i.e., cell 1 or cell 2). In this situation, eNB 1 mayallocate C-RNTI A to UE 1 that uses/operates cell 1 managed/controlledby eNB 1 as a PCell and eNB 2 may allocate C-RNTI B to UE 2 thatuses/operates cell 2 managed/controlled by eNB 2 as a PCell. Cell 2 maybe additionally allocated as a SCell to UE 1. If C-RNTI A and C-RNTIhave the same value, ambiguity occurs between a signal/channel of UE 1and a signal/channel of UE 2 in cell 2, thereby making normaltransmission/reception impossible. In this case, although RNTIs that canbe allocated to UEs may be distributed preliminarily on an eNB (cell)basis or information may be exchanged between eNBs, for allocation of anRNTI to each UE, the resulting increase in the load/latency of thebackhaul may decrease RNTI allocation efficiency.

To solve this problem, it is proposed that an independent (the same or adifferent) RNTI is allocated/used to/for each cell (aggregated) for oneUE. For example, a UE for which cell 1 and cell 2 are aggregated mayperform signal/channel transmission and reception using C-RNTI A forcell 1 and using C-RNTI B for cell 2. C-RNTI A and C-RNTI B may have thesame value or different values. Further, the UE may indicate C-RNTI Aused for cell 1 to cell 2 and C-RNTI B used for cell 2 to cell 1.Herein, cell 1 and cell 2 may be extended to cell group 1 and cell group2 and an independent RNTI may be allocated/used to/for each cell group.A cell group may include one or more cells and the same RNTI may beallocated/used to/for all cells of one cell group. An RNTIallocated/used to/for each cell may be at least one of an SI-RNTI, aP-RNTI, an RA-RNTI, a C-RNTI, an SPS C-RNTI, a temporary C-RNTI, aTPC-PUCCH-RNTI, a TPC-PUSCH-RNTI, and an MBMS RNTI (M-RNTI), preferablya C-RNTI. The cell group may be configured same or differently for eachRNTI.

FIG. 22 is a block diagram of a BS and a UE that are applicable to anembodiment of the present invention. If a wireless communication systemincludes relays, the BS or the UE may be replaced with a relay.

Referring to FIG. 22, the wireless communication system includes a BS110 and a UE 120. The BS 110 includes a processor 112, a memory 114, anda Radio Frequency (RF) unit 116. The processor 112 may be configured toperform procedures and/or methods proposed by the present invention. Thememory 114 is connected to the processor 112 and stores various types ofinformation related to operations of the processor 112. The RF unit 116is connected to the processor 112 and transmits and/or receives radiosignals. The UE includes a processor 122, a memory 124, and an RF unit126. The processor 122 may be configured to perform procedures and/ormethods proposed by the present invention. The memory 124 is connectedto the processor 122 and stores various types of information related tooperations of the processor 122. The RF unit 126 is connected to theprocessor 122 and transmits and/or receives radio signals. The BS 110and/or the UE 120 may have a single antenna or multiple antennas.

The embodiments of the present invention described above arecombinations of elements and features of the present invention inspecific forms. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present invention may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present invention may be rearranged. Someconstructions or elements of any one embodiment may be included inanother embodiment and may be replaced with corresponding constructionsor features of another embodiment. It is obvious to those skilled in theart that claims that are not explicitly cited in each other in theappended claims may be presented in combination as an embodiment of thepresent invention or included as a new claim by a subsequent amendmentafter the application is filed.

In the present disclosure, a specific operation described as performedby a BS may be performed by an upper node of the BS. Namely, it isapparent that, in a network comprised of a plurality of network nodesincluding a BS, various operations performed for communication with a UEmay be performed by the BS, or network nodes other than the BS. The term‘BS’ may be replaced with the term ‘fixed station’, ‘Node B’, ‘evolvedNode B (eNode B or eNB)’, ‘Access Point (AP)’, etc. In addition, theterm ‘terminal’ may be replaced with the term UE′, ‘Mobile Station(MS)’, Mobile Subscriber Station (MSS)′, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to exemplaryembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit is located at the interior or exteriorof the processor and may transmit and receive data to and from theprocessor via various known means. Those skilled in the art willappreciate that the present invention may be carried out in otherspecific ways than those set forth herein without departing from thespirit and essential characteristics of the present invention. The aboveembodiments are therefore to be construed in all aspects as illustrativeand not restrictive. The scope of the invention should be determined bythe appended claims and their legal equivalents, not by the abovedescription, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a wireless communication devicesuch as a UE, a relay, a BS, etc.

What is claimed is:
 1. A method for transmitting and receiving signalswith a User Equipment (UE) by a base station (BS) in a wirelesscommunication system, the method comprising: receiving informationrelated to at least one cell for transmitting Hybrid Automatic RepeatreQuest (HARQ)-ACKnowledgement (ACK); receiving downlink controlinformation (DCI) including a cell switching indication; receivingdownlink data based on the DCI; and transmitting the HARQ-ACK related tothe downlink data on a cell determined based on the cell switchingindication.
 2. The method of claim 1, wherein the cell switchingindication indicates the cell on which the HARQ-ACK related to thedownlink data is to be transmitted, among the at least one cell.
 3. Themethod of claim 1, wherein: the DCI is received via a Physical DownlinkControl Channel (PDCCH), and the downlink data is received via aPhysical Downlink Shared Channel (PDSCH).
 4. The method of claim 1,wherein the DCI includes information related to a timing relationbetween a first timing at which the downlink data is received and asecond timing at which the HARQ-ACK is transmitted
 5. A User Equipment(UE) for transmitting and receiving signals with a base station (BS) ina wireless communication system, the UE comprising: at least onetransceiver; at least one processor; and at least one computer memoryoperably connectable to the at least one processor and storinginstructions that, when executed, cause the at least one processor toperform operations comprising: receiving information related to at leastone cell for transmitting Hybrid Automatic Repeat reQuest(HARQ)-ACKnowledgement (ACK); receiving downlink control information(DCI) including a cell switching indication; receiving downlink databased on the DCI; and transmitting the HARQ-ACK related to the downlinkdata on a cell determined based on the cell switching indication.
 6. TheUE of claim 5, wherein the cell switching indication indicates the cellon which the HARQ-ACK related to the downlink data is to be transmitted,among the at least one cell.
 7. The UE of claim 5, wherein: the DCI isreceived via a Physical Downlink Control Channel (PDCCH), and thedownlink data is received via a Physical Downlink Shared Channel(PDSCH).
 8. The UE of claim 5, wherein the DCI includes informationrelated to a timing relation between a first timing at which thedownlink data is received and a second timing at which the HARQ-ACK istransmitted
 9. An apparatus for a user equipment (UE), the apparatuscomprising: at least one processor; and at least one computer memoryoperably connectable to the at least one processor and storinginstructions that, when executed, cause the at least one processor toperform operations comprising: receiving information related to at leastone cell for transmitting Hybrid Automatic Repeat reQuest(HARQ)-ACKnowledgement (ACK); receiving downlink control information(DCI) including a cell switching indication; receiving downlink databased on the DCI; and transmitting the HARQ-ACK related to the downlinkdata on a cell determined based on the cell switching indication. 10.The apparatus of claim 9, wherein the cell switching indicationindicates the cell on which the HARQ-ACK related to the downlink data isto be transmitted, among the at least one cell.
 11. The apparatus ofclaim 9, wherein: the DCI is received via a Physical Downlink ControlChannel (PDCCH), and the downlink data is received via a PhysicalDownlink Shared Channel (PDSCH).
 12. The apparatus of claim 9, whereinthe DCI includes information related to a timing relation between afirst timing at which the downlink data is received and a second timingat which the HARQ-ACK is transmitted